Like many ligand gated ion channels, glutamate receptors (GluRs) are oligomeric glycoprotein complexes composed of multiple membrane spanning subunits. The functional properties of GluRs are largely determined by the subunits that compose the receptor. For GluRs with the appropriate functional properties to form, there must exist mechanisms to regulate subunit assembly. It seems likely therefore, that GluR subunits contain highly specific interaction and recognition domains that function to regulate subunit assembly and possibly subunit stoichiometry of the receptor. The experiments proposed with in this application are aimed at identifying the association and assembly domains of both the NMDA and non-NMDA types of GluR subunits. Subunits of the nicotinic acetylcholine receptor, the inhibitory glycine and gamma-aminobutyric acid receptors contain structural domains that determine subunit stoichiometry and that are necessary for assembly of the receptor. For the subunits composing those channels, the "association domains" are located within the extracellular amino-terminus of the subunit polypeptides. The overall goal of the research proposed in this application is to identify structural domains of NMDA and non-NMDA GluR subunits that interact and that are required for the accurate assembly of functional homomeric and heteromeric receptors. Once assembly domains for the NMDA and AMPA receptor subunits are defined, assembly domain peptides will be tested for their ability to be neuroprotective during periods of EAA activated neuronal death in cultured cerebellar granule cells, a well established model system to study EAA induced neurotoxicity. The neuroprotective properties of both extracellular and intracellularly delivered GluR association domain peptides will be determined. The intracellular delivery of peptides will be facilitated by linking the association domain peptides to a 16 amino acid peptide from the third helix of the antennapedia homeodomain that is rapidly internalized by neurons. The identification of neuroprotective association domain peptides that inhibit excitotoxicity, may be the first steps toward the development of a new class of clinically important neuroprotective agents that target individual subtypes of GluRs.